Abstract: An oil pressure control device has bypass drain oil passages that bypass a control valve and that are capable of draining the engaging pressure K from a hydraulic servo of a clutch when releasing the clutch. A drain-prohibiting check ball blocks a drain path between a manual valve and an input port.

Abstract: An oil pressure control device has bypass drain oil passages that bypass a control valve and that are capable of draining the engaging pressure K from a hydraulic servo of a clutch when releasing the clutch. A drain-prohibiting check ball blocks a drain path between a manual valve and an input port.

Abstract: A compact automatic transmission for a vehicle capable of preventing increase in relative rotational speed between shift elements. A planetary gear unit is provided with a sun gear to which rotation of an input shaft is input, a carrier that can be stopped from rotating, and a ring gear for outputting, to a planetary gear set, rotation that is reduced in speed relative to that of the input shaft. A clutch is connected/disconnected, the input shaft and the sun gear are appropriately connected/disconnected, and the carrier is appropriately stopped/unstopped by a brake and a one-way clutch. This prevents relative rotational speed between shift elements of the gear unit that does not participate in a shifting operation from excessively increasing. When the clutch is disposed between the input shaft and the sun gear, the torque capacity of the clutch can be reduced as compared with the case where it is disposed between the gear unit and the gear set.

Abstract: A compact automatic transmission for a vehicle capable of preventing increase in relative rotational speed between shift elements. A planetary gear unit is provided with a sun gear to which rotation of an input shaft is input, a carrier that can be stopped from rotating, and a ring gear for outputting, to a planetary gear set, rotation that is reduced in speed relative to that of the input shaft. A clutch is connected/disconnected, the input shaft and the sun gear are appropriately connected/disconnected, and the carrier is appropriately stopped/unstopped by a brake and a one-way clutch. This prevents relative rotational speed between shift elements of the gear unit that does not participate in a shifting operation from excessively increasing. When the clutch is disposed between the input shaft and the sun gear, the torque capacity of the clutch can be reduced as compared with the case where it is disposed between the gear unit and the gear set.

Abstract: Apparatus including a pressure regulating valve for regulating line pressure for hydraulically operated frictional coupling devices of a vehicle automatic transmission, and a cut-back valve for causing the pressure regulating valve to raise the line pressure to a higher level when the transmission is placed in first-speed position, than the normal level established when the transmission is placed in any higher-gear position whose speed reduction ratio is lower than that of the first-speed position. A pressure applying device is provided to apply to the cut-back valve first and second pressures to be applied to respective two coupling devices to establish a higher-gear position of the transmission, to operate the cut-back valve for causing the pressure regulating valve to raise the line pressure to the higher level when the vehicle is started in a high-gear start mode with the transmission placed in the higher-gear position.

Abstract: A primary regulator valve has a cutback port which regulates a line pressure to increase, at the first speed of D range, a throttle pressure is applied to the cutback port through a cutback valve. The primary regulator valve sets the line pressure from a line pressure port higher. The cutback valve has a spool which is compressed in one direction. A first control chamber which is connected to a hydraulic servo (for example, a second brake hydraulic servo) which hydraulic pressure is applied at more than the second speed is formed against the pressing direction, a second control chamber which is connected to a hydraulic servo (for example, a second-coast brake hydraulic servo) to limit a coasting condition of the second speed is so formed as to follow the above pressing direction. At the second speed of second range, the cutback valve, as the first speed of D range, the throttle pressure is applied to the cutback port.

Abstract: An apparatus for controlling an automatic transmission of a motor vehicle, which has a first and a second transmission mechanism, and a testing device for testing for a shifting operation which requires shifting actions of both of the first and second transmission mechanisms. The apparatus further has a determining device for determining, based on a rotary member of the second transmission mechanism, that the shifting action of the second shifting mechanism is completed. The determining device determines that the shifting operation of the transmission is completed, at the time when a predetermined time interval has passed after the detemination that the shifting action of the second shifting mechanism is comleted. The point of time at which the completion of the shifting operation is determined may be utilized for various purposes for controlling the transmission.

Abstract: Hydraulic pressure which is regulated by a pressure control valve (linear solenoid valve) is applied to a hydraulic servo of a brake which is actuated when an engine-brake is effected. When the engine-brake is effected, a hydraulic pressure which is modulated by a modulator valve controlled by the linear solenoid valve is applied to the brake hydraulic servo. The pressure control valve provides high hydraulic pressure when vehicle speed is high based on signals from a speed sensor, and provides low hydraulic pressure when vehicle speed is low based on signals from the speed sensor, so that an engine-brake force is adequately controlled in accordance with vehicle speed. Furthermore, if a foot brake sensor is employed, the hydraulic pressure in accordance with vehicle speed can be made low when the engine-brake is effected with the foot brake applied.

Abstract: In a system for integrally controlling an automatic transmission and an engine comprising: a member for controlling the engine; a member formed separately of the engine control member, for controlling the automatic transmission; and various communication lines for connecting the engine control member and the automatic transmission control member to each other; judgments are made quickly and without fail as to whether trouble exists, such as disconnections or short-circuits of the various communication lines. When a trouble is detected, the proper control is maintained as much as possible in accordance with the types of trouble.

Abstract: A hydraulic control apparatus for controlling a hydraulically operated automatic transmission, having a speed sensor for detecting the speed of a rotary member which changes due to a shifting action of a frictionally coupling device. The apparatus includes a device for determining, based on the detected speed of the rotary member, that the shifting action of the coupling device is completed, and a device which is operated in the event of a failure of the speed sensor, for determining that the shifting action of the coupling device is completed when a time which has passed after the moment at which the need to effect the shifting action was determined or at which a shifting command to initiate the shifting action was generated exceeds a predetermined time interval. Upon determination of the completion of the shifting action, an electronic device terminates an operation to control the back pressure of an accumulator for adjusting the fluid pressure applied to the coupling device.

Abstract: In a system for integrally controlling an automatic transmission and an engine, an apparatus for controlling the automatic transmission and an apparatus for controlling the engine are formed separately from each other to reduce size and cost, and to facilitate the mounting of control means onto a vehicle. Further, if trouble occurs in this communication system between the engine control apparatus and the automatic transmission control apparatus countermeasures are properly performed, and a trouble is reduced as much as possible.

Abstract: A hydraulic control system for an automatic transmission has a shifting shock reducing device capable of regulating the transitional oil pressure applied to the frictionally engaging devices of the automatic transmission, and provided between a shift valve and the frictionally engaging devices. The shifting shock reducing device is controlled on the basis of a signal representative of the torque of the engine, and a signal representative of the transitional shift state to regulate the transitional oil pressure. Thus, the hydraulic control system is highly reliable, is capable of compensating for variations of the functions thereof over time, and is capable of maintaining a high control accuracy.

Abstract: A hydraulic hill hold control system for an automatic transmission for a vehicle adapted for the purpose of hill hold, wherein the supply of hydraulic pressure to the brake is interlocked with the shifting of the hydraulic speed stage switching system so that the brake is engaged only when the gear transmission mechanism is at a certain speed stage at which the brake is in any event engaged and therefore the engagement of the brake for hill hold does not interfere with the forward driving operation of the gear transmission mechanism.

Abstract: A hydraulic control system for an automatic transmission detects the rotating speed of the parts whose rotating speed varies due to shifting, and controls the transitional oil pressure applied to the frictionally engaging device in the automatic transmission so that the detected rotating speed matches the locus of the target rotating speed that said parts should follow after the shift command is outputted. Thus, the optimum shifting transitional characteristics can be obtained regardless of the inherent differences among otherwise identical vehicles which differences are created at the time of manufacturing or vary with time and vehicle use.

Abstract: A central differential device for differentially transmitting rotational power from the engine to the front wheel propeller shaft and the rear wheel propeller shaft in a vehicle is locked up step by step to restrict its differential operation gradually when the difference between front wheel rotational speed and rear wheel rotational speed is larger than a reference value while checking at each step before further increasing the degree of locking up if the difference is still larger than the reference value which may be changed for such each step.

Abstract: A selecting valve is provided, which is switched by different signals sent out when the vehicle is stopped or when the vehicle is to start to move. The selecting valve is connected to a hydraulic servo unit for a forward clutch which is engaged to transmit torque when the vehicle is to move forward, and is supplied with line pressure and a control pressure provided by an electronically operated regulating valve, such as an electronically controlled throttle valve. The regulated control pressure from the electronically operated regulating valve is supplied to the hydraulic servo unit for the forward clutch when the vehicle is stopped, while line pressure is supplied when the vehicle is to move, thus preventing creeping and shift shock at starts. Since the selecting valve is provided with a port leading to the hydraulic servo unit for a brake which restricts vehicle movement, the brake can be applied when the vehicle is stopped and released when moved, thus providing hill-holding capability.

Abstract: In a system for integrally controlling an automatic transmission and an engine wherein engine torque is changed during shifting, it is detected whether or not various communication means provided for carrying out the engine torque change is in a failed state. If so, a shift parameter or parameters in the automatic transmission, such as a shift point and engagement oil pressure, are changed in a direction for securing the durability of frictionally engaging devices. When the shift point is changed, a measured value of factors for determining the shift point is corrected to substantially lower the shift point. With this arrangement, computer capacity can be decreased.

Abstract: In a full time type four wheel drive power transmission system having a planetary gear mechanism for dividing input power supplied to the carrier into a first output power delivered from the sun gear for one pair of four wheels and a second output power delivered from the ring gear for another pair of four wheels or directly connecting the sun gear and the ring gear to the carrier by selectively rotationally connecting the sun gear and the ring gear by a clutch, the ring gear and the casing of the clutch are respectively provided with a series of teeth or other surface projections or unevenness, and two sensors are provided respectively to detect each unevenness for detecting rotational speed of the sun gear and the ring gear.

Abstract: In a four wheel drive vehicle, this torque distribution device includes a friction engaging mechanism which controls drive torque distribution to the front vehicle wheels and/or to the rear vehicle wheels, and a servo device which receives an actuating hydraulic fluid pressure and which applies an engaging force to the friction engaging mechanism so as to cause it to be able to transmit torque. The engaging force for the friction engaging mechanism and the maximum torque transmission capacity thereof this provided both increase monotonically according to increase of the actuating hydraulic fluid pressure. This servo device includes first and second pistons which partially serve to define respective first and second pressure chambers, and which, when impelled by hydraulic fluid pressure in their respective first and second pressure chambers, both provide such engaging force for the friction engaging mechanism.

Abstract: A vehicle includes an engine and an automatic transmission which has a fluid torque converter, a forward clutch, and a manual range setting valve. Idling control for providing anti creep control is performed by, during engine idling time while the manual range setting valve is set to a forward driving range and the vehicle is substantially stationary, reducing the engagement pressure of the forward clutch by reducing the actuating pressure provided to it. A rotational speed associated with the fluid torque converter is detected, and the actuating pressure provided to the forward clutch is controlled so that the rotational speed associated with the fluid torque converter does not drop below a certain rotational speed value. Thereby good anti creep control is provided. A system is also disclosed for performing the method.